Managing Databases with Oracle Questions and Answers

Q: What is the type of Oracle backup in which all uncommitted changes have been removed from the datafiles?

Correct answer: Consistent backupA consistent backup is taken with the database cleanly shut down, so every datafile is at the same system change number and no uncommitted change remains in it. It can be restored without applying redo. An inconsistent backup is taken with the database open and does require redo to be applied before it can be used.

Q: Oracle directly supports the definition of surrogate keys.

Correct answer: FalseOracle has no declaration that makes a column a surrogate key. The usual construction is a sequence to generate the values together with a trigger that assigns the next value on insert, or in later versions an identity column, but neither is a direct definition of a surrogate key in the sense the statement claims.

Q: After a table has been created, its structure can be modified using the SQL command:

Correct answer: ALTER TABLE [ TableName ].ALTER TABLE is the standard command for changing an existing table - adding or dropping a column, changing a datatype, adding or removing a constraint. UPDATE changes data rather than structure, and the other two are not SQL commands at all.

41.

What is the type of Oracle backup in which all uncommitted changes have been removed from the datafiles?

A.Full backup
B.Consistent backup
C.Inconsistent backup
D.Differential backup

Answer: B

Correct answer: Consistent backup

A consistent backup is taken with the database cleanly shut down, so every datafile is at the same system change number and no uncommitted change remains in it. It can be restored without applying redo. An inconsistent backup is taken with the database open and does require redo to be applied before it can be used.

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42.

Oracle directly supports the definition of surrogate keys.

A.True
B.False

Answer: B

Correct answer: False

Oracle has no declaration that makes a column a surrogate key. The usual construction is a sequence to generate the values together with a trigger that assigns the next value on insert, or in later versions an identity column, but neither is a direct definition of a surrogate key in the sense the statement claims.

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43.

After a table has been created, its structure can be modified using the SQL command:

A.UPDATE TABLE [TableName].
B.MODIFY TABLE [TableName].
C.ALTER TABLE [TableName].
D.CHANGE TABLE [TableName].

Answer: C

Correct answer: ALTER TABLE [ TableName ].

ALTER TABLE is the standard command for changing an existing table - adding or dropping a column, changing a datatype, adding or removing a constraint. UPDATE changes data rather than structure, and the other two are not SQL commands at all.

Discuss in Forum

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Managing Databases with Oracle Questions and Answers

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